Post on 27-Jun-2020
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-0.5 0 0.5 1 1.5 2 2.5 3 3.5CNT wt%
Foam_TopFoam_BottomComposite_TopComposite_Bottom
Surf
ace
Con
duct
ivity
(1/O
hm)
GOALI/Collaborative Research: Fabrication of Ultra-light Multifunctional Nanofoams from Polymer NanocompositesGrant No.: CMMI-0728287NSF Program: NM/GOALI
Introduction High performance polymer nanocomposites
• Taking advantages of excellent inherent properties of high performance polymer matrices
• Improved mechanical, thermal, and electrical properties by adding nano-additives in the polymer matrix
Nanofoams have benefits of foamed materials• Light-weight products• Thermal insulation and sound-proof properties• Higher strength-to-weight ratio
Combining the benefits of high performance polymer nanocomposites and nanofoams• Light-weight, multifunctional materials with excellent mechanical,
thermal, and electrical properties for various applications• Possible higher and more effective electromagnetic interference
shielding property while maintaining inherent excellent mechanical and thermal properties of high performance polymer
Objectives To develop an innovative fabrication approach to multifunctional nanofoams from high performance
polymeric nanocomposites To study the envisioned multi-functionality of high performance nanocomposite nanofoam materials,
such as high electrical conductivity and low density with inherent excellent properties of the polymer matrix.
Conclusions The PEI/CNT foams showed significantly improved electrical conductivity satisfying the ANSI/ESD
standard for dissipative materials with reduced density. It is expected that the PEI/CNT foams can serve as light-weight electronics protection materials under
high temperature and stress due to its multifunctionality. The PEI/CNT nanofoams were fabricated with the pore size of under 100 nm. Further characterizations
are needed to demonstrate the property improvement for nanofoams compared to microfoams.
Acknowledgements- Graduate students Nick Vaccaro, Jeremy Barker, Emmanuel Cua, and Yongha Kim. - Dr. Edmond Kung at SABIC for providing PEI.
Results Solvent extraction effect on volumetric electrical
conductivity of nanocomposites
• Residual solvent contents : 12-14% - Weaken mechanical and thermal properties• No notable effect of residual solvent on the electrical conductivity
Volume conductivity of composites and foams
• Volume conductivity satisfies the ANSI/ESD(2008) for dissipative materials• ANSI/ESD(2008) criteria for dissipative materials: 1E-11 to 1E-4 (S)
Surface conductivity of composites and foams
PI: Wei Li, Department of Mechanical Engineering, University of Texas at AustinCo-PI: Samra Sangari, Boeing Commercial Airplanes, The Boeing Company
Anti-static
Electromagnetic interferenceshielding
Lightning strike mitigation
Experimental The high pressure solid state foaming process
Sample preparation• Functionalized MWCNTs from Cheap Tubes, Inc.• Ultem PEI 1010P provided by SABIC Innovative
plastics. • PEI/CNT composites preparation
− Solvent casting (Solvent: DCM)
Temperature Controller
CO2 Tank Pressure Vessel
Stage I Saturation
Stage IIFoamingDesorption
Syringe Pump
Properties Values
Density 1.28 g/ccTensile Strength, Ultimate 114 MPa
Tensile Modulus 3.45 GpaElectrical conductivity 1e-17 S/cm
Dielectric Constant 3.15Glass Transition Tg 216 °CStable Service Temperature ~170°C
Polymer matrix (PEI)
Factors Values
CNT wt% 0.5 – 3wt% (0.5wt% interval)Saturation pressure 8 MPaSaturation time 24 hoursFoaming temperature 175 CFoaming time 20 seconds
Factors in the experiment
02468
10121416
0 0.5 1 1.5 2 2.5 3
Mas
s Lo
ss P
erce
ntag
e
CNT wt%
Mass loss by ScCO2 after Vacuum Oven treatment
Mass loss by Vacuum Oven treatment
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Volu
me
Con
duct
ivity
(S/C
m)
CNT wt%
Before VO
After VO
After ScCO2
Relative density of foams
• Significant density reduction was achieved by foaming
SEMs
• Dispersed CNTs were found throughout the polymer matrix for both unfoamed and foamed samples
• Pore sizes were around 1 micrometer• Bonding between CNTs and the matrix needs to be improved to
maximize the additive effect (Future research)
0
10
20
30
40
50
60
0 0.5 1 1.5 2 2.5 3
Relativ
e Den
sity (%
)
CNT wt%
1E-181E-171E-161E-151E-141E-131E-121E-111E-101E-091E-081E-071E-061E-05
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Volu
me
Con
duct
ivity
(S/C
m)
CNT wt%
CompositesFoams
2.85E-08
1.30E-13
1.88E-12
1.09E-10
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Unfoamed Foamingcondition-1
Foamingcondition-2
Foamingcondition-3
DC
Con
duct
ivity
(S/c
m)
0 wt% Pure PEI
(195 , 2) (195, 30) (175, 30) (Temp(C), Time(sec))
• Surface conductivity for foams satisfies the ANSI/ESD(2008) for dissipative materials
• Conductivities of bottom surfaces were higher than that of top surfaces
Data from previous study with CNF
Unfoamed Foamed
0wt% CNT
1.5wt% CNT
3wt% CNT
Scale bars: 2 µm
• Saturation conditions: 8MPa, 24hours• Foaming conditions: 195C, 20 sec in glycerol bath
Scale bars: 1 µm
CNTs
Nanofoamed PEI/CNT(0.5wt%) nanocomposite(Pore size:~100nm)